During the course of well drilling operations, a wall of a wellbore being drilled is generally sealed and stabilized by means of a protective steel casing which is lowered through a wellbore. Afterwards, the casing is cemented in place after retrieval of the drilling assembly. Setting a steel casing in a well is a time consuming and expensive procedure. Since the wellbore is essential to removing desired fluids from a subterranean formation, it is necessary that the wellbore's casing remain intact to make for a more efficient operation and avoid the loss of wellbore fluids into the formation.
Often during the production of hydrocarbonaceous fluids or other desired fluids from a formation via a wellbore, the wellbore becomes damaged or corroded. The damage may be caused by excessive pressure within the wellbore which will cause a section of wellbore casing to fail thereby interfering with its integrity. Also, wellbores which are located at levels in excess of about 5,000 ft. will often have an environment where high temperatures, high pressures, and corrosive chemicals are encountered. When these chemicals, pressures and temperatures combine, casing corrosion often occurs thereby necessitating the repair of a section of the casing so as to maintain its integrity thereby avoiding a loss of desired fluids into the formation.
Depending upon the composition of the casing which is used in the wellbore, the expense of replacing the wellbore's casing can vary. When stainless steel casings are used for example, replacement costs can be substantial. For these reasons, it is desirable to have a method for repairing the casing in the wellbore so as to maintain the efficiency of operations for removing desired fluids from the formation while at the same time minimizing downtime and repair costs. Heretofore, it has been necessary to remove the entire wellbore casing and replace it with new casing. This of course is a time consuming and expensive operation.
Often the wellbore is filled with fluids, particularly brine, which interfere with the integrity of many gel systems utilized for zone isolation. During zone isolation, the integrity of a subsequently formed gel or blocking agent is compromised by enhanced oil recovery (EOR) operations which employ steam, hydrocarbonaceous fluids, water, or carbon dioxide. Carbon dioxide can cause a gel or blocking agent, such as cement, to deteriorate in an acid environment which shortens its life and minimizes its effectiveness. Low temperatures encountered in some formations also keep some gels or blocking agents from making effective gels or blocking agents.
Therefore, what is needed is a simple and inexpensive method for zone isolation, and repair or replacement of a wellbore casing in situ so as to avoid loss of operational time, the production of desired fluids from the formation, or diversion of injection fluids to the oil-bearing formation when low temperatures or acidic conditions are encountered.